Substance transfer device

ABSTRACT

A work station for simultaneously performing multiple assays includes a base structure, a receptacle rack assembly received within a receptacle rack well formed in the base structure, a pipette tip rack assembly received within a pipette tip rack well formed in the base structure, a multiple conduit substance transfer device, and substance transfer device positioning structure. The receptacle rack assembly holds a plurality of receptacles in which a plurality of individual assays are performed, and the pipette tip rack assembly holds a plurality of contamination limiting pipette tips. The substance transfer device is capable of simultaneously dispensing substances into two or more receptacles or simultaneously removing substances from two or more receptacles. Alternatively, the substance transfer device is capable of simultaneously dispensing substances into two or more receptacles, and, at about the same time, simultaneously removing substances from two or more receptacles. The positioning structure permits the substance transfer device to be positioned with respect to the receptacle rack assembly or the pipette tip rack assembly.

This application is a continuation of Ser. No. 09/826,944 filed Apr. 6,2001, which is a divisional of Ser. No. 09/191,343 filed Nov. 13, 1998,now U.S. Pat. No. 6,254,826, which in turn claims the benefit of U.S.Provisional Application No. 60/065,798 filed Nov. 14, 1997.

FIELD OF THE INVENTION

The present invention features a work station useful for simultaneouslyperforming multiple biological assays in a manner that minimizes thepotential for cross-contamination between individual assays.

BACKGROUND OF THE INVENTION

None of the references described or referred to herein are admitted tobe prior art to the claimed invention.

Diagnostic assays are widely used in clinical diagnosis and healthscience research to detect or quantify the presence or amount ofbiological antigens, cell abnormalities, disease states, anddisease-associated pathogens, including parasites, fungi, bacteria andviruses present in a host organism or sample. Where a diagnostic assaypermits quantification, practitioners may be better able to calculatethe extent of infection or disease and to determine the state of adisease over time. In general, diagnostic assays are based either on thedetection of antigens (immunoassays) or nucleic acids (nucleicacid-based assays) belonging to an organism or virus of interest.

Nucleic acid-based assays generally include several steps leading to thedetection or quantification of one or more target nucleic acid sequencesin a sample which are specific to the organism or virus of interest. Thetargeted nucleic acid sequences can also be specific to an identifiablegroup of organisms or viruses, where the group is defined by at leastone shared sequence of nucleic acid that is common to all members of thegroup and is specific to that group in the sample being assayed. Thedetection of individual and groups of organisms and viruses usingnucleic acid-based methods is fully described by Kohne, U.S. Pat. No.4,851,330, and Hogan, U.S. Pat. No. 5,541,551.

The first step in a nucleic acid-based assay is designing a probe whichexhibits specificity, under stringent hybridization conditions, for anucleic acid sequence belonging to the organism or virus of interest.While nucleic acid-based assays can be designed to detect eitherdeoxyribonucleic acid (DNA) or ribonucleic acid (RNA), ribosomal RNA(rRNA), or the gene encoding rRNA (rDNA), is typically the preferrednucleic acid for detection of a prokaryotic or eukaryotic organism in asample. Ribosomal RNA target sequences are preferred because of theirrelative abundance in cells, and because rRNA contains regions ofsequence variability that can be exploited to design probes capable ofdistinguishing between even closely related organisms. (Ribosomal RNA isthe major structural component of the ribosome, which is the situs ofprotein synthesis in a cell.) Viruses, which do not contain rRNA, andcellular changes are often best detected by targeting DNA, RNA, or amessenger RNA (mRNA) sequence, which is a nucleic acid intermediate usedto synthesize a protein. When the focus of a nucleic acid-based assay isthe detection of a genetic abnormality, then the probes are usuallydesigned to detect identifiable changes in the genetic code, such as theabnormal Philadelphia chromosome associated with chronic myelocyticleukemia. See, e.g., Stephenson et al., U.S. Pat. No. 4,681,840.

When performing a nucleic acid-based assay, preparation of the sample isnecessary to release and stabilize target nucleic acids which may bepresent in the sample. Sample preparation can also serve to eliminatenuclease activity and remove or inactivate potential inhibitors ofnucleic acid amplification (discussed below) or detection of the targetnucleic acids. See, e.g., Ryder et al, U.S. Pat. No. 5,639,599, whichdiscloses methods for preparing nucleic acid for amplification,including the use of complexing agents able to complex with ferric ionscontributed by lysed red blood cells. The method of sample preparationcan vary and will depend in part on the nature of the sample beingprocessed (e.g., blood, urine, stool, pus or sputum). When targetnucleic acids are being extracted from a white blood cell populationpresent in a diluted or undiluted whole blood sample, a differentiallysis procedure is generally followed. See, e.g., Ryder et al., EuropeanPatent Application No. 93304542.9 and European Patent Publication No.0547267. Differential lysis procedures are well known in the art and aredesigned to specifically isolate nucleic acids from white blood cells,while limiting or eliminating the presence or activity of red blood cellproducts, such as heme, which can interfere with nucleic acidamplification or detection.

Before or after exposing the extracted nucleic acid to a probe, thetarget nucleic acid can be immobilized by target-capture means, eitherdirectly or indirectly, using a “capture probe” bound to a substrate,such as a magnetic bead. Examples of target-capture methodologies aredescribed by Ranki et al., U.S. Pat. No. 4,486,539, and Stabinsky, U.S.Pat. No. 4,751,177. Target capture probes are generally short sequencesof nucleic acid (i.e., oligonucleotide) capable of hybridizing, understringent hybridization conditions, with a sequence of nucleic acidwhich also contains the target sequence. Magnets in close proximity tothe reaction vessel are used to draw and hold the magnetic beads to theside of the vessel. Once the target nucleic acid is thus immobilized,the hybridized nucleic acid can be separated from non-hybridized nucleicacid by aspirating fluid from the reaction vessel and optionallyperforming one or more wash steps.

In most instances, it is desirable to amplify the target sequence usingany of several nucleic acid amplification procedures which are wellknown in the art. Specifically, nucleic acid amplification is theenzymatic synthesis of nucleic acid amplicons (copies) which contain asequence that is complementary to a nucleic acid sequence beingamplified. Examples of nucleic acid amplification procedures practicedin the art include the polymerase chain reaction (PCR), stranddisplacement amplification (SDA), ligase chain reaction (LCR), andtranscription-associated amplification (TAA). Nucleic acid amplificationis especially beneficial when the amount of target sequence present in asample is very low. By amplifying the target sequences and detecting theamplicon synthesized, the sensitivity of an assay can be vastlyimproved, since fewer target sequences are needed at the beginning ofthe assay to better ensure detection of nucleic acid in the samplebelonging to the organism or virus of interest.

Methods of nucleic acid amplification are thoroughly described in theliterature. PCR amplification, for instance, is described by Mullis etal. in U.S. Pat. Nos. 4,683,195, 4,683,202and 4,800,159, and in Methodsin Enzymology, 155:335-350 (1987). Examples of SDA can be found inWalker, PCR Methods and Applications, 3:25-30 (1993), Walker et al. inNucleic Acids Res., 20:1691-1996 (1992) and Proc. Natl. Acad. Sci.,89:392-396 (1991). LCR is described in U.S. Pat. Nos. 5,427,930 and5,686,272. And different TAA formats are provided in publications suchas Burg et al. in U.S. Pat. No. 5,437,990; Kacian et al. in U.S. Pat.Nos. 5,399,491 and 5,554,516; and Gingeras et al. in InternationalApplication No. PCT/US87/01966 and International Publication No. WO88/01302, and International Application No. PCT/US88/02108 andInternational Publication No. WO 88/10315.

Detection of a targeted nucleic acid sequence requires the use of aprobe having a nucleotide base sequence which is substantiallycomplementary to the targeted sequence or, alternatively, its amplicon.Under selective assay conditions, the probe will hybridize to thetargeted sequence or its amplicon in a manner permitting a practitionerto detect the presence of the targeted sequence in a sample. Effectiveprobes are designed to prevent non-specific hybridization with anynucleic acid sequence which will interfere with detecting the presenceof the targeted sequence. Probes may include a label capable ofdetection, where the label is, for example, a radiolabel, fluorescentdye, biotin, enzyme or chemiluminescent compound. Chemiluminescentcompounds include acridinium esters which can be used in a hybridizationprotection assay (HPA) and then detected with a luminometer. Examples ofchemiluminescent compounds and methods of labeling probes withchemiluminescent compounds can be found in Arnold et al., U.S. Pat. Nos.4,950,613, 5,185,439 and 5,585,481; and Campbell et al., U.S. Pat. No.4,946,958.

HPA is a detection method based on differential hydrolysis which permitsspecific detection of the acridinium ester-labeled probe hybridized tothe target sequence or amplicon thereof. HPA is described in detail byArnold et al. in U.S. Pat. Nos. 5,283,174 and 5,639,599. This detectionformat permits hybridized probe to be distinguished from non-hybridizedprobe in solution and includes both a hybridization step and a selectionstep. In the hybridization step, an excess of acridinium ester-labeledprobe is added to the reaction vessel and permitted to anneal to thetarget sequence or its amplicon. Following the hybridization step, labelassociated with unhybridized probe is rendered non-chemiluminescent inthe selection step by the addition of an alkaline reagent. The alkalinereagent specifically hydrolyzes only that acridinium ester labelassociated with unhybridized probe, leaving the acridinium ester of theprobe:target hybrid intact and detectable. Chemiluminescence from theacridinium ester of the hybridized probe can then be measured using aluminometer and signal is expressed in relative light units (RLU).

After the nucleic acid-based assay is run, and to avoid possiblecontamination of subsequent amplification reactions, the reactionmixture can be treated with a deactivating reagent which destroysnucleic acids and related amplification products in the reaction vessel.Such reagents can include oxidants, reductants and reactive chemicalswhich modify the primary chemical structure of a nucleic acid. Thesereagents operate by rendering nucleic acids inert towards anamplification reaction, whether the nucleic acid is RNA or DNA. Examplesof such chemical agents include solutions of sodium hypochlorite(bleach), solutions of potassium permanganate, formic acid, hydrazine,dimethyl sulfate and similar compounds. More details of a deactivationprotocol can be found in Dattagupta et al., U.S. Pat. No. 5,612,200.

When performed manually, the complexity and shear number of processingsteps associated with a nucleic acid-based assay introduce opportunitiesfor practitioner-error, exposure to pathogens, and cross-contaminationbetween assays. Following a manual format, the practitioner must safelyand conveniently juxtapose the test samples, reagents, waste containers,assay receptacles, pipette tips, aspirator device, dispenser device, andmagnetic rack for performing target-capture, while being especiallycareful not to confuse racks, test samples, assay receptacles, andassociated tips, or to knock over any tubes, tips, containers, orinstruments. In addition, the practitioner must carefully performaspirating and dispensing steps with hand-held, non-fixed instruments ina manner requiring precise execution to avoid undesirable contactbetween assay receptacles, aerosol formation, or aspiration of magneticparticles or other substrates used in a target-capture assay. As afurther precaution, the magnetic field in a manually performedtarget-capture assay is often applied to only one side of the assayreceptacle so that fluids can be aspirated through a pipette tipinserted along the opposite side of the assay receptacle. Althoughapplying a magnetic field to only one side of the assay receptacle is aless efficient means for performing a target capture assay, it isdesigned to prevent magnetic particles from being unnecessarilyaspirated as a result of practitioner inaccuracies.

Although the specific number and types of steps performed may varybetween assays, the risks of error, pathogen exposure andcross-contamination in executing the steps involved in all nucleicacid-based assays is a constant concern and requires that practitionersattain a significant level of skill and dexterity. Moreover, therepetitive nature of the steps involved in a nucleic acid-based assayoften leads to physical discomfort or injury, such as carpal tunnelsyndrome, for those practitioners who perform high volumes of thesetypes of assays on a daily basis. Particularly affected arepractitioners working in health care laboratories, where thepractitioner's sole or primary responsibility is to conduct diagnosticassays.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a work station according to the presentinvention;

FIG. 2 is an exploded perspective view of a work station according tothe present invention;

FIG. 3 is a perspective view of the base structure of a work stationaccording to the present invention;

FIG. 4 is an exploded perspective view of a contamination limitingelement holding structure in the form of a removable pipette tip rackand pipette tip holding cassettes for use in a work station according tothe present invention;

FIG. 5 is an exploded perspective view of a receptacle holding structurein the form of a removable receptacle rack for use in a work stationaccording to the present invention;

FIG. 6 is a plan view of the base structure and substance transferdevice positioning structure of a work station of the present invention;

FIG. 7 is a cross-section of the work station of FIG. 1 taken along theline “VII-VII”;

FIG. 8 is a side elevation of a cassette for holding a plurality ofpipette tips;

FIG. 9 is a top view of the cassette structure;

FIG. 10 is a cross-section of the cassette structure in the direction“X-X” in FIG. 8;

FIG. 11 is a cross-section of the cassette structure in the direction“XI-XI” in FIG. 9;

FIG. 12 is a side elevation of an alternate cassette for holding aplurality of pipette tips and a cooperating cover for the cassette;

FIG. 13 is transverse cross-section of the cassette of FIG. 12;

FIG. 14 is a side elevation, partially in cross-section of a substancetransfer device adapted for use with the work station of the presentinvention;

FIG. 15 is a perspective view of an alternate embodiment of a workstation according to the present invention;

FIG. 16 is a front elevation of an alternate embodiment of a substancetransfer device adapted for use with a work station according to thepresent invention; and

FIG. 17 is a side elevation of the substance transfer device of FIG. 16.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT

For convenience in the following description, various directional orother spatial references are made with regard to the orientation ofstructure(s) shown in the drawings. It is understood, however, that suchreferences, including, without limitation, upper, lower, top, bottom,front, back, left, right, vertical, horizontal, lateral, orlongitudinal, are made for convenience only and should not necessarilybe construed to be limiting on the invention described herein.

A work station for simultaneously performing multiple biological assaysis designated generally by 20 in FIGS. 1 and 2. The work station 20includes a base 100 preferably having a rectangular profile when viewedfrom the top and having a top surface 160 and integral front, back, andside walls (see FIG. 3) on which instructions or other indicia may beapplied. The base 100 is preferably formed of a plastic material andmore preferably of a reaction injection molded polyurethane.

Base 100 includes a first purge/prime trough 150 which comprises anelongated depression 152 formed in base 100 surrounded by a peripheralupstanding wall 154 extending around depression 152 above the topsurface of base 100. In the illustrated embodiment, a second purge/primetrough 190 comprises an elongated depression 192 formed in base 100surrounded by a peripheral upstanding wall 194 extending arounddepression 192 above the top surface of base 100. The second purge/primetrough 190 is optional. The purge/prime troughs 150, 190 are preferablyremovable from the base 100 so that any fluids in the troughs can beeasily emptied and the troughs can be cleaned. In addition, thepurge/prime troughs are preferably covered with a conforming stopper, orcap, when not in use to keep out environmental contaminants and tominimize evaporation. The purpose of the first and second purge/primetroughs 150, 190 will be described below.

A base knob 156 is attached at the head of a threaded pin extending intoa threaded receiving aperture in the side of the base 100. A similarknob and threaded pin are provided on the opposite side of the base 100.An optional bottom plate (not shown) extends across the bottom of base100 and includes two upstanding tabs formed at opposite sides of theplate. The tabs have centrally-located apertures formed therein, and theplate is secured to the bottom of the base 100 by aligning the aperturesformed in the tabs with the receiving apertures and inserting thethreaded pins through the tab apertures and turning them into theirrespective threaded receiving apertures.

A receptacle holding assembly 200 is provided on one side of the base100. The receptacle holding assembly 200 holds a plurality ofreceptacles 262, preferably in the form of reaction tubes, such as, forexample, test tubes, as shown in the illustrated embodiment. Thereceptacles are preferably oriented in an array comprising a number ofrows, with each receptacle being presented in an operative orientationwhich allows substances, such as fluids, to be dispensed into and/orremoved from two or more receptacles simultaneously.

A contamination limiting element holding assembly 300 for holding aplurality of contamination limiting elements 362, e.g. pipette tips asshown in the illustrated embodiment, is provided on another side of thebase 100 adjacent the receptacle holding assembly 200. The individualelements 362 are held by the assembly 300, preferably in an arraycomprising a number of rows of pipette tips, so as to be presented in anoperative orientation so that two or more of the pipette tips may besimultaneously engaged and removed from the holding assembly 300 andsubsequently be simultaneously disengaged and replaced into the assembly300. The contamination limiting element holding assembly 300 alsopreferably secures each individual pipette tip so as to substantiallyprevent its contacting adjacently held pipette tips to avoidcross-contamination therebetween.

Work station 20 further includes a substance transfer device 400 whichcan simultaneously dispense or withdraw substances from two or more ofthe plurality of receptacles held in the receptacle holding assembly200. Most preferably, substance transfer device 400 can simultaneouslydispense substances into two or more receptacles of one row ofreceptacles while simultaneously or alternatively removing substancesfrom two or more receptacles of another row of receptacles. Thesubstance transfer device can also simultaneously engage and remove twoor more of the pipette tips held in the contamination limiting elementholding assembly 300 when the substance transfer device is moved intooperative proximity with the contamination limiting element holdingassembly 300.

Work station 20 also includes a substance transfer device positioningstructure 500 for accurately positioning the substance transfer device400 over either the receptacle holding assembly 200 or the contaminationlimiting element holding assembly 300. The positioning structure 500facilitates accurate and repeatable positioning of the substancetransfer device 400 with respect to the contamination limiting elementholding assembly 300 so that two or more pipette tips of a row ofpipette tips can be simultaneously engaged by the substance transferdevice 400 and removed from the contamination limiting element holdingassembly 300 or so that two or more pipette tips engaged by thesubstance transfer device 400 can be simultaneously disengaged by thesubstance transfer device 400 and replaced in the contamination limitingelement holding assembly 300. Similarly, the positioning structure 500facilitates accurate and repeatable positioning of the substancetransfer device 400 with respect to the receptacle holding assembly 200so that the substance transfer device 400 can simultaneously dispensesubstances into and/or withdraw substances from two or more receptaclesof a row of receptacles held in the receptacle holding assembly 200.Additionally, the positioning structure 500 provides standby positionsfor storing the substance transfer device during periods of non-use.

With primary reference to FIGS. 2, 3, 6, and 7, the receptacle holdingassembly 200 includes a receptacle rack well 102 formed in the base 100and being of a generally rectangular shape. A plurality of lateraldividing walls 104 extending across the bottom of well 102 definelaterally extending troughs 106. A plurality of protrusions 108, whichextend vertically and are longitudinally-spaced along opposite sides ofthe lateral dividing walls 104, define structure for holding individualreceptacles, whose ends are disposed within troughs 106, apart from oneanother.

Magnets 112, shown in phantom in FIG. 7, may be disposed within thewalls 104. The magnets are preferably formed from Neodymium-Iron-Boron(NdFeB) grade n-37, have an individual size of 0.5×0.5×0.3 inches. Suchmagnets are provided to impart a magnetic force on solutions containingmagnetic particles within receptacles disposed between the walls 104 forcertain magnetic separation procedures as will be described in moredetail below.

The receptacle rack well 102 preferably includes four upstanding supportcolumns 114, 116, 118, and 120 proximate the four corners of the well102. Support columns 114-120 may be integrally molded within the well102 of the base 100 and preferably have a generally rectangularcross-sectional shape.

Hand wells 122 and 124 are provided on opposite ends of the receptaclerack well 102 and are disposed between columns 114, 116 and between 118,120, respectively. The receptacle rack well 102, including the dividingwalls 104, and the support columns 114-120 provide a receiving structurefor accommodating a removable receptacle holding device, such asreceptacle holding structure 201 described below.

With reference to FIGS. 2 and 5, the receptacle holding assembly 200includes a receptacle holding structure 201 which comprises a removablereceptacle rack 202. The rack 202 includes generally parallel sidewalls204 and 206 and end wall structures 208 and 210. Four upstanding supportcolumns 220, 222, 224, 226 preferably extend from four corners of a topportion of rack 202 for supporting thereon an optional rack cover member(not shown). A plurality of equidistantly spaced, generally parallelcross members 212 extend laterally across rack 202 from sidewall 204 toside wall 206. Also, a plurality of equidistantly spaced, generallyparallel dividing members 214 extend longitudinally between adjacentcross members 212 to define a plurality of receptacle receiving boxframes 216.

Preferably, nine equidistantly spaced cross members 212 are providedbetween end wall structures 208, 210, and preferably, nine equidistantlyspaced dividing walls 214 extend between adjacent cross members 212 fromside wall 204 to side wall 206. Accordingly, the cross members 212 anddividing members 214 define ten lateral rows often receptacle receivingbox frames 216.

Receptacle rack 202 is preferably sized and configured so as to fiteasily and removably within the receptacle rack well 102 of the basestructure 100. Rack 202 is supported within the well 102 by means of thesupport columns 114, 116, 118, and 120 extending into hollow cavitiesdefined by end wall structures 208, 210.

Finger well 218 formed in end wall structure 208 and a similar fingerwell (not shown) formed in end wall structure 210 cooperate with thehand wells 122 and 124 of the base structure 100 and facilitate removaland replacement of the rack 202 from and into the receptacle rack well102.

As an alternative to the removable structure described above, anon-removable structure similar to rack 202 in construction may befixedly secured within well 102 or a receptacle holding structure may beformed integrally within base 100.

In the preferred embodiment, the receptacle holding structure 201further includes receptacle holding panels 240, which may be removablymounted within each row defined by cross members 212. Each panel 240includes a plurality of apertures 242 formed therein, each aperturebeing aligned with one box frame 216 of receptacle rack 202 when thepanel 240 is mounted to the rack 202. The size, number, and shape of theapertures formed in a panel can be varied so as to accommodate a varietyof different sizes, shapes, and numbers of receptacles. Accordingly, thereceptacle rack 202 may accommodate a variety of different types andsizes of receptacles as well as various numbers of receptacles, merelyby placing different receptacle holding panels 240 therein. In thepreferred embodiment of the receptacle rack 202, however, ten receptaclereceiving box frames 216 are provided in each row defined by crossmembers 212. Thus, it can be appreciated that in the preferredembodiment, each panel 240 can accommodate a maximum of ten receptacles.

Each receptacle holding panel 240 is preferably removably held within anassociated row of rack 202 by means of attaching structure which maycomprise tabs 244 extending upwardly from opposite ends of each row ofrack 202 which may lockingly engage mating slots 246 formed in the endsof panel 240. Of course, the positions of the tabs and the mating slotscould be reversed. That is, tabs could extend from panel 240 whichoperatively engage mating slots formed in receptacle rack 202.

Each receptacle holding panel 240 holds a plurality of individualreceptacles 262, in a row 260. Preferably, receptacle rack 202 can holdten receptacles in each of the ten rows, for a total capacity of onehundred receptacles.

It is within the contemplated scope of the present invention to providea single removable panel, having an array of receptacle receivingapertures formed therein, which removably covers the entire upperportion of receptacle rack 202. Alternatively, a non-removable panelhaving an array of receptacle receiving apertures formed therein may befixedly secured to receptacle rack 202 or integrally formed with rack202.

While the drawings show individual, removable receptacles, i.e., testtubes, used in the work station, a modular receptacle structure in whicha plurality of receptacles and a holding panel are integrally molded ofa suitable material, such as plastic, is preferred. The modularstructure may comprise a linear or matrix array of receptacles which areintegrally formed with and connected to one another via the holdingpanel. It is also contemplated that some combination of removable,individual receptacles and grouped and/or nonremovable receptacles maybe used as well.

When receptacle rack 202, having a plurality of receptacles 262 disposedtherein, is placed into the receptacle rack well 102, the lower ends ofthe receptacles are received between walls 104 in the troughs 106 ofwell 102. The spacing between adjacent walls 104 is preferably such thatthe receptacles may be received therebetween with a minimum offrictional contact between the receptacles and the walls 104. Inaddition, the spacing between adjacent protrusions 108 corresponds tothe spacing between adjacent dividing members 214 so that theprotrusions 108 cooperate with the box frames 216 and apertures 242 ofreceptacle holding panels 240 to hold each individual receptacle in agenerally upright orientation and separated from adjacent receptacles.

With primary reference to FIGS. 2, 3, 6, and 7, the contaminationlimiting element holding assembly 300 includes a pipette tip rack well140 which may be integrally formed within the base 100 and whichpreferably defines a generally rectangular shape. The pipette tip rackwell 140 provides a receiving structure for accommodating a removablecontamination limiting element holding device, such as contaminationlimiting element holding structure 301 described below. Upwardlyextending supporting end walls 142, 144 are formed on opposite sides ofthe well 140 and extend from the top surface 160 of the base 100.Centrally located registration pins 146, 148 preferably extend from atop central portion of each of the end walls 142, 144, respectively.

With primary reference to FIGS. 2, 4, and 7, the contamination limitingelement holding assembly 300 further includes a contamination limitingelement holding structure 301, which comprises a removable pipette tiprack 302. Removable pipette tip rack 302 includes opposed, generallyparallel upstanding side walls 304 and 306 with a top panel 308extending therebetween. The removable rack 302 can be supported on itsopposed side walls 304, 306 on a surface when the rack is removed fromthe pipette tip rack well 140. A plurality of equidistantly spaced,generally parallel slots 310 extend laterally across top panel 308.Further, registration apertures 316, 318 are centrally formed inopposite ends of the top panel 308.

Removable pipette tip rack 302 is removably disposed in an operativeorientation within pipette tip rack well 140. With the removable pipettetip rack 302 installed within the pipette tip rack well 140, the toppanel 308 rests upon and is supported by the support end walls 142, 144and the registration apertures 316, 318 receive the registration pins146, 148, respectively, so as to insure the proper disposition of theremovable rack 302 within well 140. It can appreciated, however, thatthe positions of the pins and the apertures can be reversed. That is, adownwardly extending pin may be provided on the top panel 308 whichwould be received within a mating aperture formed in the tops of theupwardly extending support end walls 142, 144. In addition, more thanone registration pin and mating aperture may be provided on each endand/or on the sides of the pipette tip rack well 140. Moreover, otherregistration means, such as the pipette tip rack 302 fitting snuglywithin pipette tip rack well 140 with little clearance, may be used toaccurately position the pipette tip rack 302.

Raised edge portions 312, 314 are preferably formed along opposite endsof the top panel 308. Edge portions 312, 314 facilitate the grasping ofthe rack 302 for removing the rack 302 from the well 140 and installingthe rack 302 into the well 140 and further provide surfaces forsupporting an optional pipette tip rack cover (not shown).

As an alternative to the removable structure described above, anon-removable structure similar in construction to rack 302 may befixedly secured within well 140 or a pipette tip holding structure maybe formed integrally within base 100.

In the preferred embodiment, the contamination limiting element holdingstructure 301 further includes one or more cassettes 340 for holdingindividual contamination limiting elements 362. Each cassette 340 isreceived by and removably secured within an associated one of the slots310 formed in top panel 308 of rack 302.

As shown in FIGS. 8-11, cassette 340 comprises an elongated uprightstructure defined by generally parallel side walls 342, 344 connected atopposite ends thereof by end walls 346, 348 which may bearcuately-shaped, as shown. A top panel 350 extends across the top ofthe cassette and includes a plurality of aligned apertures 352, each forreceiving an individual pipette tip. The ends of top panel 350 extendbeyond end walls 346, 348 so as to define shoulders 366, 368. Eachcassette 340 preferably includes ten aligned apertures 352 for holdingup to ten protective pipette tips 362 in a row 360, and top panel 308preferably includes ten laterally extending slots 310. Thus, the entirepipette tip rack 302 preferably accommodates up to one hundred pipettetips 362 disposed in ten rows 360.

An upper wall 354 extends about the top panel 350 proximate the outeredge thereof. Preferably, however, top panel 350 extends peripherallybeyond upper wall 354 so as to define an upwardly facing peripheralshoulder 364. A plurality of equidistantly spaced, generally paralleldividing walls 356 extend from one side wall 342 to the opposite sidewall 344 for dividing the cassette 340 into a plurality of pipette tipholding compartments 358. Each of the apertures 352 opens into a one ofthe compartments 358. The cassette 340 shown in the drawings has nobottom wall so that the bottom end of each compartment 358 is open, butthe bottom end of each compartment may, alternatively, be sealed.

A pipette tip 362 includes an upper portion 363 having a larger diameterthan a lower portion 365, thereby defining an annular shoulder betweenthe upper portion 363 and the lower portion 365 which engages theperipheral edge of aperture 352 to prevent the pipette tip 362 fromfalling through the cassette 340.

Each cassette 340 may include coupling structure which cooperates withassociated coupling structure formed in the top panel 308 of the rack302 for removably attaching the cassette 340 to the top panel 308.Preferably, however, each cassette is placed into a slot 310 in the rack302 with shoulders 366, 368 of cassette 340 extending beyond the slot310 and the cassette being held into slot 310 by its own weight.

The cassette 340 is preferably made of a suitable plastic material, andmost preferably a polypropylene, and the dividing walls 356, side walls342, 344, and end walls 342, 344, are preferably tapered so as tofacilitate the forming thereof by a molding technique.

An alternate, and preferred, cassette 600 is shown in FIGS. 12 and 13.The cassette 600 includes a plurality of pipette tip-receiving tubes 604which are preferably slightly tapered. The tubes 604 are equidistantlyspaced and are preferably oriented generally in parallel with eachother. In the preferred embodiment, as shown in the figures, cassette600 includes ten pipette tip-receiving tubes 604. Each of the individualtubes 604 is connected to one another by a connecting structure, such asthin web 606 extending between adjacent tubes 604.

A panel 609 extends across the length of cassette 602, connecting thetop portions of the pipette tip-receiving tubes 604. An upwardlyextending, continuous wall 616 extends from the panel 609. Panel 609defines an upwardly facing ledge 614 and a downwardly facing ledge 612.Side ribs 608 and front and back ribs 610 (only the front ribs arevisible) are formed on the side and the front and back, respectively, ofthe end-most tubes 604, extending down from the panel 609. Each cassette600 fits into one of the slots 310 of the pipette tip rack 302, with thedownwardly facing ledge 612 being supported on the portion of top panel308 peripherally surrounding the slot 310. Preferably, three 90°-spacedgrooves (not shown) are formed at each end of slot 310 extending awayfrom slot 310. The three ribs 608 and 610 formed on each of the endtubes 604 of the cassette 600 mate with the three grooves to stabilizethe cassette 600 within slot 310. Risers 618 extend upwardly from thepanel 609 and facilitate grasping of the cassette 600 to remove thecassette from the pipette tip rack 302. A cover member 602 fits over thetop of the cassette 600 and is supported on the upwardly facing ledge614. Cover member 602 includes a wide lower portion 603 whichaccommodates the upwardly extending wall 616 and a narrowed upperportion 605.

As shown in FIG. 13, the inner portion of each pipette tip-receivingtube 604 includes a channel 630 that is preferably tapered. A raisedsurface 620 extends above the panel 609 across the tops of the channels630. Openings defining frustoconical surfaces 634 are formed in theraised surface 620. The frustoconical surfaces 634 taper inwardly towardan opening 632 of each channel 630. An annular shoulder 636 extendsabout the periphery of each opening 632 at the base of the frustoconicalsurface 634.

Each channel 630 receives an associated pipette tip 650 having a taperedlower portion 652 and an upper portion 654 of generally larger diameterthan the lower portion 652. An annular shoulder 656 is defined about thebase of the enlarged upper portion 654. When the pipette tip 650 isinserted into the channel 630, shoulder 656 of the pipette tip engagesthe shoulder 636 of the associated pipette tip-receiving tube 604,thereby limiting the extent to which the pipette tip 650 is insertedinto the channel 630. The lower portion 652 of the pipette tip 650 has alength that is generally less than the length of the channel 650 belowthe annular shoulder 636, so that the bottom tip 658 does not contactthe bottom 631 of the channel 630. The frustoconical surfaces 634 helpalign the pipette tips 650 with the openings 632 when the pipette tipsare being lowered into the cassette 600.

Cassette 600 is preferably injection molded from an appropriate,non-reacting thermoplastic.

A removable drip tray (not shown) may be provided at the base of thepipette tip rack well 140 for collecting drippings from pipette tip 362held within the cassettes 340 disposed within pipette tip rack 302,especially if cassettes having no bottom walls are used. In this way,the potential for contamination is even further limited.

Rather than the removable cassettes described above, it is within thecontemplated scope of the present invention to provide a non-removable,or partially removable structure for receiving the pipette tips. Forexample, top surface 308 of rack 302 may have an array of pipettetip-receiving openings formed therein, and a pipette tip separatingstructure for preventing pipette tips from contacting one another, suchas dividing walls or an egg-crate type structure, may be provided inwell 140 below top surface 308, or such a separating structure may beprovided as an integral component of rack 302.

With reference to FIGS. 1, 2, 7, and 12, the work station 20 furtherincludes a substance transfer device 400, preferably a multiple conduitpipetter/aspirator device for dispensing and removing substances,typically fluids, to and from two or more receptacles simultaneously orsequentially. The substance transfer device 400 comprises an elongatedhorizontal frame member 402 with two upstanding handles 404, 406projecting upwardly from opposite ends of the frame member 402 to whichhandles 404, 406 may be attached by suitable mechanical fasteners or thelike. Handles 404, 406 may include buttons 460, 462, preferably disposedat top portions thereof. Buttons 460, 462 are coupled through handles404, 406, respectively, to a pipette tip disengaging plate 430, disposedon the underside of frame member 402 and preferably formed fromstainless steel.

Two guide rods 408, 410 extend downwardly beneath the frame member 402from opposite ends thereof, generally below the handles 404, 406. Guiderods 408, 410 are preferably generally parallel with one another and maybe attached to frame member 402 by suitable mechanical fasteners or thelike. Coil springs 470, 472 are preferably disposed on guide rods 408,410 extending below frame member 402. Springs 470, 472 are preferablyinstalled by a push fit into counter bores 409, 411, respectively,formed in the frame 402 coaxially with the rods 408, 410. The purposeand function of the guide rods 408, 410 and the springs 470, 472 will bedescribed in more detail below.

In the embodiment illustrated in FIGS. 1 and 2, the substance transferdevice includes a substance dispensing apparatus 441 carried on theframe member 402 and constructed and arranged to dispense substancesinto two or more receptacles simultaneously and a substance removingapparatus 421 also carried on the frame member 402 and constructed andarranged to removed (e.g., by aspiration) substances form two or morereceptacles simultaneously.

In the preferred embodiment, the substance removing apparatus 421includes an aspirator manifold 420 operatively supported on the framemember 402 between the handles 404, 406. Aspirator manifold 420 definesa central conduit 422 which divides into a plurality, preferably ten, ofbranch conduits 424. Each of the branch conduits 424 has an extensionportion 426 extending therefrom and through a slot 432 formed in pipettetip disengaging plate 430. A flexible tube 428, preferably formed of aplastic material, or other suitable conduit structure, extends from thecentral conduit 422 of the aspirator manifold 420. Tube 428 may beconnected to a container (not shown) in which aspirated fluids can bestored. Alternatively, the substance removing apparatus 421 of thesubstance transfer device 400 may include a portable storage containercarried thereby for holding aspirated substances therein.

The substance dispensing apparatus 441 includes a dispenser manifold440, also operatively supported on frame member 402 between the handles404, 406. Dispenser manifold 440 defines therein a central conduit 442which divides into a plurality of branch conduits 444. A flexible tube448, preferably formed of a plastic material, or other suitable conduitstructure, extends from the central conduit 442 of the dispensermanifold 440 and may be connected to a container (not shown) whichstores substances to be dispensed into receptacles. Substances arepreferably supplied from a remote storage container to the substancetransfer device 400 via tube 448 by a hand pump (not shown) calibratedto withdraw a predetermined amount of substance from the storagecontainer for dispensing the predetermined amount into the receptaclesthrough the dispenser manifold 440. Substances may be supplied from astorage container to dispenser manifold 440 by a separate metering pumpmechanism (not shown) which could be operated by a hand or foot switch.A preferred dispensing pump is a 10 ml bottle top dispenser availablefrom Wheaton under the trade name “Calibrex 520.” Alternatively, aportable substance container may be provided on substance transferdevice 400.

Although the substance transfer device 400 illustrated in FIGS. 1 and 2includes both a substance removing apparatus 421 and a substancedispensing apparatus 441, the substance transfer device may includeeither a substance removing apparatus or a substance dispensingapparatus. Moreover, a single work station may include more than onesingle-function substance transfer device, e.g., a substance-removingsubstance transfer device and a substance-dispensing substance transferdevice. Alternatively, a single substance transfer device more includemore than one substance removing apparatuses and/or more than onesubstance dispensing apparatuses.

With primary reference to FIGS. 1, 2, 6, and 7, the work station 20,further includes a substance transfer device positioning structure 500comprised of three elongated guide supports 502, 504, 506. Each of theguide supports 502-506 is preferably made from Delrin and is attached toa top portion 160 of the base 100, guide support 502 being attachedalong a first edge 162 of the base 100, guide supports 506 beingattached along an opposite edge 164, and guide support 504 beingattached at top portion 166 between the receptacle rack well 102 and thepipette tip rack well 140.

Each of the guide supports 502, 504, 506 may be attached to the base 100by any suitable means, such as for example mechanical fastener elements.Alternatively, guide supports 502-506 may be integrally molded with thebase 100, may be attached to the base 100 by a suitable adhesive, or maybe fixed to the base 100 by cooperating attaching structures formed onthe base and the individual guides.

The guide supports 502-506 are preferably identical in construction,having a plurality of longitudinally-spaced aligned guide holes 510,512, 514, respectively, formed therein. A plurality oflongitudinally-spaced aligned guide holes 170, 172, 174 are formed intop portions 162, 166, 164, respectively, of base 100. Holes 510 alignand cooperate with holes 170 when guide support 502 is attached to topportion 162, holes 512 align and cooperate with holes 172 when guidesupport 504 is attached to top portion 166, and holes 514 align andcooperate with holes 174 when guide support 506 is attached to topportion 164. In addition, each of the holes 510, 512, 514 is laterallyaligned with an adjacent corresponding hole formed in the other guidesupports.

Each of the guide supports 502, 504, 506 preferably includes fourteenguide holes 510, 512, 514, respectively. The middle twelve guide holesconstitute dispensing and aspirating guide holes. Of the twelvedispensing and aspirating guide holes, the middle ten are aligned withassociated rows of receptacles and pipette tips held in their respectiveholding structures. The first and twelfth guide holes precede the firstrows of receptacles and pipette tips and follow the last rows ofreceptacles and pipette tips, respectively.

Each of the guide supports 502-506 also preferably includes standbyholes 524, 526, 528, respectively, formed near opposite ends of therespective guide supports. The stand-by holes 524, 526, and 528 alignand cooperate with associated holes 176, 178, 180, respectively, formedin top portions 162, 166, 164, respectively, of base 100. The purposeand functions of the dispensing and aspirating guide holes and thestandby guide holes will be described in more detail below.

Guide supports 502 and 504, together with their respective, associatedguide holes 510, 512, comprise a contamination limiting elementregistration structure that is constructed and arranged to register, orposition, the substance transfer device with respect to thecontamination limiting element holding assembly 300. Guide supports 504and 506, together with their respective, associated guide holes 512,514, comprise a receptacle registration structure that is constructedand arranged to register, or position, the substance transfer device 400with respect to the receptacle holding assembly 200. The guide rods 408,410 of the substance transfer device 400 comprise a transferregistration structure that is constructed and arranged to beselectively engaged with either the receptacle registration structure orthe contamination limiting element registration structure in a manner tobe described below.

Although the work station 20 preferably includes both a receptacleholding assembly 200 and a contamination limiting element holdingassembly 300, so that both receptacles and pipette tips are provided inthe same work space and because many assays require pipette tips inaddition to receptacles, it is within the contemplation of the broaderaspects of the present invention to provide a work station having only areceptacle holding assembly with a substance transfer device andsubstance transfer device positioning structures provided in associationwith the receptacle holding assembly. Such a truncated work stationcould still provide substantial benefits over prior art methods andapparatuses as it would allow accurate, repeatable, and simultaneousdispensing of substances into and/or withdrawing of substances from twoor more receptacles disposed in the receptacle holding assembly.

Operation of the preferred embodiment of the work station of the presentinvention will now be described.

The substance transfer device is preferably initially stored in astandby position, with guide rods 408, 410 inserted into the standbyholes 526, 528, respectively or 524, 526, respectively, located ateither end of the guide supports. The exact standby position is notcritical.

The receptacle holding assembly 200 is configured for performing assaysby placing a receptacle rack 202 into the receptacle rack well 102 inbase 100. Receptacle holding panels 240 are installed into each of oneor more rows defined by the cross members 212 of the rack 202. A numberof receptacles 262, corresponding to the number of assays to beperformed, is inserted into the apertures 242 of the receptacle holdingpanels 240 until each receptacle is properly seated between the walls104 in the receptacle rack well 102. In the preferred embodiment of thework station, integral receptacle/holding panel modules are operativelyinstalled into the receptacle rack 202. In the case of biologicalassays, each receptacle will typically already contain specimen samplematerial, which may be derived from, for example, sputum, cervicalswabs, blood, urine, puss, or stool, and each receptacle may be suitablymarked to identify the specimen sample source and/or to identify theassay or assays to be performed on the specimen sample.

It is not critical that the receptacle rack 202 be first placed into thereceptacle rack well 102. The receptacle holding panels 240 and/or thereceptacles 262 may be placed into the rack 202 before rack 202 isplaced into well 102.

The contamination limiting element holding assembly 300 is configuredfor performing assays by placing the pipette tip rack 302 into thepipette tip rack well 140 with each of the registration pins 146, 148properly inserted into a mating registration aperture 316, 318,respectively. A number of contamination limiting pipette tips 362,preferably corresponding to the number of receptacles 262 installed inthe receptacle rack 202, is inserted into the pipette tip rack 302.

The pipette tips 362 preferably come pre-packaged, for instance, in acassette 340 of ten pipette tips. A cover member may be provided in theform of an elongated cap which fits over upper wall 354 and contacts theperipheral shoulder 364 of the cassette 340 to cover the pipette tipsheld therein and prevent them from falling out of the cassette duringtransport and storage of the cassettes. Each cassette is also preferablywrapped in a hermetically sealed film. To set up the contaminationlimiting element holding assembly 300, a desired number of cassettes maybe unwrapped, uncovered, and installed into the slots 310 of the pipetterack 302.

It is not critical that the pipette tip rack 302 be first placed intothe pipette tip rack well 140. The cassettes 340 may be placed into therack 302 before the rack is placed into well 140.

With the receptacle holding assembly 200 and the contamination limitingelement holding assembly 300 thus set up, substances, such as reagentsor buffer solutions, may be added to each of the receptacles 362 held inthe receptacle holding assembly 200 by the substance transfer device400.

The substance transfer device 400 is removed from a stand-by positionand placed over the first row of receptacles, with guide rods 408, 410aligned with the associated guide hole 512 of guide support 504 andguide hole 514 of guide support 506, respectively, to align thedispenser manifold 440 with the first row of receptacles such that eachbranch conduit 444 of the dispenser manifold 440 is operatively alignedwith an associated one receptacle position (i.e., with an associatedreceptacle receiving box frame 216 of the receptacle rack 202) in thefirst row. In the illustrated embodiment, ten branch conduits 444 areprovided for up to ten receptacles in each row. It is contemplated,however, that less than ten receptacles may be placed in any row, andthe extra branch conduits can be capped off.

In the illustrated embodiment, the aspirator manifold 420 is centered onthe substance transfer device 400, i.e., arranged in series with theguide rods 408, 410, and the dispenser manifold 440 is offset fromcenter by a distance equal to the spacing between adjacent rows 260 ofreceptacles, which is preferably also the spacing between adjacent rows360 of pipette tips. Alternatively, the dispenser manifold 440 may becentered on the substance transfer device 400 and the aspirator manifold420 may be offset, or neither manifold may be centered on the substancetransfer device.

With the preferred embodiment, in which the aspirator manifold 420 iscentered and the dispenser manifold 440 is offset, however, tooperatively align the dispenser manifold 440 with a row of receptacles,the guide rods 408, 410 must be inserted into the guide holes 512, 514aligned with the following row of receptacles. Thus, to align thedispenser manifold 440 with the first row of receptacles, the guide rodsmust be inserted into the third hole of each of the pluralities of holes512, 514, i.e., into the second of the twelve dispensing and aspiratingguide holes. In addition, to align the dispenser manifold 440 with thelast row of receptacles, assuming that one-hundred receptacles 262 areheld in the receptacle rack 202, the guide rods must be inserted intothe second to last hole of each of the pluralities of holes 512, 514,i.e., into the twelfth dispensing and aspirating guide holes which arenot aligned with the last row of receptacles. To accommodate proceedingalong the rows of receptacles from either direction, a nonaligneddispensing and aspirating guide hole is provided on either end of theten guide holes aligned with rows of receptacles and pipette tips. Thus,twelve guide holes are preferred.

With the dispenser manifold 440 properly aligned, the substance transferdevice 400 is then lowered with respect to the guide supports 504, 506.As best shown in FIG. 7, guide holes 510, 512, 514 include counter-boredportions 511, 513, 515, respectively, for accommodating the springs 470,472. As the substance transfer device 400 is lowered with respect to theguide supports 504, 506, springs 470, 472 are received withincounter-bores 513, 515, respectively. The lengths of springs 470, 472are longer than the lengths of counter-bores 513, 515, so that positivedownward pressure must be applied to the substance transfer device 400to cause the springs 470, 472 to compress within counter bores 513, 515until the main frame member 402 of the substance transfer device 400 isproperly seated on the guide supports 504, 506. The springs 470, 472provide for a smooth, controlled descent of the substance transferdevice 400 toward the guide supports 504, 506 and avoids sudden impactbetween substance transfer device 400 and guide supports 504, 506 shouldthe substance transfer device be dropped. The dispenser conduit 340 ispreferably constructed so that, with the substance transfer device 400fully lowered over a row of receptacles, no portion of the branchconduits 344 contacts an associated receptacle. With the substancetransfer device thus properly positioned, substance dispensing ispreferably controlled by a calibrated hand pump but can be controlled bya non-integral pump which can be actuated by a hand or foot switch.

Because, as will become more apparent shortly, the guide rods 408, 410of the substance transfer device are repeatedly inserted into andremoved from the guide holes 510, 512, 514, it is preferred that theguide holes 510, 512, 514, and especially the twelve dispensing andaspirating guide holes, be elliptical in shape so as to provide a smallamount of play between the guide rods and the guide holes and thusprevent binding when the rods 408, 410 are moved in and out of theholes. Because the standby holes 524, 526, 528 are not repeatedly used,and to limit movement of the substance transfer device 400 when it is ina standby position, the standby holes 524, 526, 528 are preferably roundin shape, providing a snug fit between the guide rods and the standbyholes.

Next, the substance transfer device is manually lifted until the rods408, 410 clear the holes 512, 514 associated with the first row ofreceptacles. The substance transfer device 400 is then manually indexedforward one row of receptacles and the rods 408, 410 are inserted intothe next associated holes 512, 514 to operatively align the dispensermanifold 440 with the next row of receptacles. The substance transferdevice 400 is then lowered until the main frame member 402 is seatedatop the guide supports 504 and 506, and the next row of receptacles isthen filled with a desired substance or substances.

These steps are repeated until the desired reaction substance orsubstances have been added to all of the receptacles disposed in thereceptacle holding assembly 200. One or both purge/prime troughs 150,190 can be used as a depository for excess fluids in the substancetransfer device.

The substance transfer device is then replaced in a standby position.The standby holes 524, 526, 528 are preferably placed at opposite endsof the guide supports 502, 504, 506 so that the substance transferdevice 400 can be placed in a standby position before the first row ofpipette tips or receptacles or after the last row of pipette tips orreceptacles and also to accommodate operation of the substance transferdevice from either direction.

The guide holes, and especially the dispensing and aspirating guideholes, may be color-coded or marked with appropriate alpha-numericindicia to aid in accuracy and to further avoid the chance of dispensingand aspirating errors.

At this point, depending on the requirements of the particular assaybeing performed, the receptacle rack 202 may be lifted out of thereceptacle rack well 102 and placed on a shaker mechanism to shake theentire rack 202 to mix the contents of each of the receptacles heldtherein. Alternatively, or in addition, the rack may be placed in anincubator. Following a mixing and/or incubating procedure, thereceptacle rack 202 may be replaced into the receptacle rack well 102.If, following the addition of magnetic particles use to capture targetmaterials (i.e, nucleic acids), a magnetic separation procedure is to beperformed in the assay, and magnets are provided in the walls 104 of thereceptacle rack well 102, the rack would be allowed to set in thereceptacle rack well 102 undisturbed for an appropriate period of timewith the receptacles and the fluids contained therein exposed to themagnetic field, as required by the magnetic separation procedure.

Following appropriate assay steps, the next assay step may require theremoval of some or all of the liquid contents, e.g., supernatant, ofeach of the receptacles by aspiration. To begin the aspiration sequence,the substance transfer device 400 is removed from the standby positionand is placed over the contamination limiting element holding assembly300 with the guide rods 408 and 410 inserted into the appropriate guidehole 510 of guide support 502 and guide hole 512 of guide support 504,respectively, to operatively align the aspirator manifold 420 with afirst row of contamination limiting pipette tips 362 held in thecontamination limiting element holding assembly 300, such that each ofthe branch conduits 424 of the aspirator manifold 420 is aligned with anassociated pipette tip in the row. The substance transfer device 400 isthen lowered toward the guide supports 502, 504. As the substancetransfer device 400 is lowered with respect to the guide supports 502,504, springs 470, 472 are received within counter-bores 511, 513,respectively. The lengths of springs 470, 472 are longer than thelengths of counter-bores 511, 513, so that positive downward pressuremust be applied to the substance transfer device 400 to cause thesprings 470, 472 to compress within counter bores 511, 513 until themain frame member 402 of the substance transfer device 400 is properlyseated on the guide supports 502, 504. The springs 470, 472 provide fora smooth, controlled descent of the substance transfer device 400 towardthe guide supports 504, 506 and avoids sudden impact between substancetransfer device 400 and guide supports 502, 504 should the substancetransfer device be dropped.

At this point, the extension portion 426 of each of the branch conduits424 engages an associated one of the pipette tips in the first row ofpipette tips. Preferably, each branch conduit engages an associatedpipette tip by the extension portion 426 thereof extending into theupper opening of the pipette tip element so as to frictionally engagethe pipette tip when the main member 402 of the substance transferdevice 400 is seated on the guide supports 502 and 504.

When the substance transfer device is lifted off the guide supports 502,504, each of the pipette tips 362 in the first row, held onto anassociated extension portion 426 of the aspirating manifold 420 byfriction, is lifted out of its holding compartment 358 of the firstcassette 340.

Next, the substance transfer device 400 is positioned above thereceptacle holding assembly 200 with the aspirator manifold 420operatively aligned with the first row of receptacles held in thereceptacle holding assembly 200 so that each pipette tip 362 held ontoan associated extension portion 426 of the aspirator manifold 420 isaligned with an associated receptacle in the first row of receptacles.

Guide rods 408, 410 preferably extend lower than the bottom ends of thepipette tip 362 held onto the aspirator manifold 420 so that the rods408, 410 engage the appropriate guide holes 512, 514 to properly alignthe substance transfer device 400 with the row of receptacles before thepipette tips held on the substance transfer device are brought intoproximity with the receptacles. With the rods 408, 410 initiallyinserted into the appropriate guide holes 512, 514 for aligning thepipette tips held thereon with the first row of receptacles, thesubstance transfer device 400 is lowered, thus inserting each of thepipette tips engaged thereby into an associated receptacle until themain member 402 of the substance transfer device 400 is seated on theguide supports 502 and 506.

The contamination limiting pipette tips 362 limit potentiallycontaminating contact between the contents of each receptacle and theexterior surface of the extensions 426 of the aspirator manifold 420because only the pipette tip, and not the extension 426 itself, isinserted into the receptacle. Such contamination limiting pipette tipsare typically not necessary for dispensing substances into thereceptacles because it is not necessary for any portion of the dispensermanifold 440 to be inserted into the receptacle to thereby expose thedispenser manifold 440 to the potentially contaminating contentsthereof.

With the substance transfer device 400 seated on the guide supports 504,506 and the pipette tips fully inserted into the receptacles, some orall of the contents of each receptacle is aspirated through anassociated pipette tip. The substance transfer device is operativelycommunicated with a vacuum source (not shown) to provide suction foraspirating substances through the pipette tip and the aspirator manifold420. The preferred vacuum source is a Gast oil-free laboratory vacuumpump, model DOPAO104AA, having a specified vacuum capacity to 25 in Hg,and manufactured by Gast Manufacturing of Benton Harbor, Mich. Theaspirated fluid is transferred, by receptacle 428, preferably to a wastecontainer.

After each of the receptacles in the first row of receptacles isaspirated, the substance transfer device 400 is manually lifted untilthe guide rods 408, 410 clear the associated guide holes 512, 514, andthe substance transfer device 400 is then moved over the contaminationlimiting element holding assembly 300 so that the aspirator manifold 420is operatively aligned with the first, now empty, cassette in thepipette tip holding rack 302. Again, the lengths of the rods 408, 410ensure that the rods enter the associated holes 510, 512, respectively,so that the aspirator manifold 420 is properly aligned with the firstcassette and each pipette tip is aligned with an associated aperture 352in the cassette before the substance transfer device is lowered. Withthe guide rods 408, 410 initially inserted into the guide holes 510, 512associated with the first cassette, the substance transfer device islowered until the frame member 402 is seated on the guide supports 502,504 and each pipette tip is inserted through an associated aperture 352into an associated pipette tip holding compartment 358. The pipette tipsare then disengaged from the extensions 426 of the aspirator manifold420 by pressing the buttons 460, 462 to actuate the pipette tipdisengaging plate 430 by moving the plate 430 downwardly with respect toframe member 402 to the position shown in phantom in FIG. 14. Pipettetip disengaging plate 430 has formed therein an elongated slot 432through which extensions 426 of aspirator manifold 420 extend. The widthof the slot formed in plate 430 is large enough to accommodate theextension elements 426 but is smaller than the outside diameter of thetop of each pipette tip 362. Thus, when pipette tip disengaging plate430 moves downwardly, the edges of slot 432 contact the pipette tipsheld onto the extensions 426 and push the pipette tips off theextensions. (see FIG. 14). As an alternative to elongated slot 432,plate 430 could have formed therein a plurality of individual aperturescorresponding in number and position to the extensions 426 of aspiratormanifold 420, wherein the width of each aperture is large enough toaccommodate an associated extension element 426 but is smaller than theoutside diameter of the top of each pipette tip 362.

The substance transfer device is then lifted until the guide rods 408,410 clear the guide holes 510, 512 and the substance transfer device isthen indexed forward one row. With the guide rods 408, 410 inserted intothe guide holes 510, 512 associated with the next row, or cassette, ofpipette tips, the device is lowered until the frame member 402 is seatedon guide supports 502, 504 and the extensions 426 of the aspiratormanifold 420 engage associated pipette tips in the next row of pipettetips in the same manner as the first row of pipette tips was engaged bythe aspirator manifold 420.

The substance transfer device is then lifted away from the contaminationlimiting element holding assembly 300, with the next row of pipette tipsfrictionally held thereon, and moved into alignment with the next row ofreceptacles to be aspirated in the receptacle holding assembly 200 byinserting guide rods 408, 410 into the guide holes 512, 514 associatedwith the next row of receptacles. With the substance transfer device 400properly positioned so that the aspirator manifold 420 is operativelyaligned with the next row of receptacles, the substance transfer device400 is lowered until the frame member 402 is seated on the guidesupports 504, 506 and each of the pipette tips held on the aspiratormanifold 420 is operatively inserted into each associated receptacle ofthe next row of receptacles. Thus, some or all of the contents containedin each of the receptacles in the next row can be aspirated through thepipette tips and the aspirator manifold 420.

The dispenser manifold 440 is offset from the aspirator manifold 420 sothat, with the aspirator manifold 420 operatively aligned with the nextrow of receptacles, the dispenser manifold 440 is operatively alignedwith the previous row of receptacles from which some or all of thecontents has already been aspirated in the preceding aspirationsequence. Thus, assuming that the assay calls for the dispensing ofadditional substance(s) into the receptacles after the first aspiration,additional substance can be added to each receptacle in the precedingrow of receptacles, preferably at about the same time that substance isbeing aspirated from each receptacle in the following row ofreceptacles.

The substance transfer device 400 is then lifted, moved back to thecontamination limiting element holding assembly 300 to replace thepipette tips engaged therewith into their respective row, or cassette,indexed forward to engage a next row of pipette tips, and moved back tothe receptacle holding assembly 200 to aspirate a next row ofreceptacles and optionally dispense substance into a preceding row ofreceptacles from which some or all of the contents thereof has beenaspirated in the previous aspiration sequence.

The sequences are repeated until all of the rows of receptacles havebeen aspirated and, optionally, all but the last row of receptacles hasbeen refilled by the dispenser manifold 440. After the last row ofpipette tips has been replaced in its respective row, or cassette, thesubstance transfer device is moved back to the receptacle holdingassembly 300 and positioned so that the dispenser manifold 440 isoperatively aligned with the last row of receptacles, i.e., the guiderods 408, 410 are inserted into the twelfth dispensing and aspiratingguide holes, which are not aligned with the last row of receptacles, andsubstance is then dispensed into the last row. After the last row ofreceptacles is filled, the substance transfer device 400 is again placedin a standby position. Alternatively, all rows may be aspirated beforestarting the dispense operation.

Again, depending on the requirements of the particular assay beingperformed, the receptacle rack 202 may be placed on a mixing device orin an incubator, and/or the receptacles may be subjected to a magneticfield within the receptacle rack well 102, or other steps may beperformed.

If further aspirating and dispensing is required, the rack 202 can bereplaced into the receptacle rack well 102 and the above-described stepsof aspirating and dispensing can be performed with the substancetransfer device until all receptacles have been aspirated and thenfilled.

Note that it is possible to sequentially and repeatably engage the firstrow of pipette tips, aspirate the first row of receptacles, replace thefirst row of pipette tips, engage the second row of pipette tips,aspirate a second row of receptacles, etc., so that each individualcontamination limiting pipette tip is associated with and used with onlyone individual receptacle. After one set of receptacles has been fullyprocessed using the work station 20, the associated set of pipette tipsis discarded and fresh receptacles and fresh pipette tips are installedbefore commencing with the next sequence of assays.

An embodiment of single-function substance transfer device (i.e., asubstance dispensing device or a substance removing device) isdesignated generally by reference number 800 in FIGS. 16 and 17. Thesubstance transfer device 800 includes a transversely extending,elongated frame member 804 with guide rods 806 and 808 extendingdownwardly from opposite ends of the frame member 804. Guide rods 806and 808 serve the same function and operate in the same manner as guiderods 408, 410 of the substance transfer device 400 described above inthis specification.

A single handle 802 extends upwardly from a central portion of the framemember 804 and, as shown in FIG. 17, is preferably oriented at a slightangle (e.g., approximately 10 degrees) with respect to vertical. Thesubstance transfer device also includes a manifold 812 defining acentral conduit (not shown) and a plurality (preferably ten) of branchconduits (not shown) for engaging two or more of the receptacles and/orcontamination limiting elements in a row. A flexible tube 810 extendingfrom the handle 802 is in communication with the central conduit of themanifold 812 for transmitting substances (e.g., fluids) to or from themanifold 812.

It can be appreciated that if only a single-function substance transferdevice is used with the assay work station, the guide supports need onlyinclude guide holes which align with each of the rows of receptacles, aswell as stand-by holes, if desired. That is, the guide rods 806, 808 ofthe single function substance transfer device 800 can be aligned withthe manifold 812, so that it is not necessary to dispense substance intoor remove substance from a row of receptacles that is off center withrespect to the guide rods 806, 808, as with the dual function device 400described above in which the dispenser manifold 440 is off center withrespect to the guide rods 408, 410.

Although substance transfer device 800 may constitute either a substancedispensing device or a substance removing device, it is preferably asubstance dispensing apparatus. That is because a substance removingdevice would normally be used in conjunction with contamination limitingelements, and therefore the device would also preferably include apipette tip disengaging plate, such as pipette tip disengaging plate 430of substance transfer device 400, and the pipette tip disengaging plateis preferably actuated by means of buttons, such as buttons 460 and 462of substance transfer device 400, provided in each of a pair of handles.Thus, a single handled device, such as that shown in FIGS. 16 and 17 isbetter suited for use as a substance dispensing device, which istypically not used in conjunction with contamination limiting elementswhich need to be disengaged after use.

An alternate embodiment of a work station according to the presentinvention is designated generally by reference number 1000 in FIG. 15.As with the work station 20 described above, work station 1000 includesa base 100, a receptacle holding assembly 200, and a contaminationlimiting element holding assembly 300. Station 1000 includes asingle-function, substance dispensing, substance transfer device 700 anda single-function, substance removing, substance transfer device 720.The dispensing substance transfer device 700 includes an elongated framemember 702, two upstanding handles 704, 706, and a dispensing manifold708, with an associated conduit-tube 710. Similarly, the substanceremoving substance transfer device 720 includes an elongated framemember 722, two upstanding handles 724, 726, and an aspirator manifold728, with an associated conduit-tube 730. Substance removing substancetransfer device 720 also includes buttons 760, 762 for activating apipette tip disengaging plate (not shown) similar to pipette tipremoving plate 430 of substance transfer device 400 described above.Either substance transfer device 700 or 720, but especially dispensingsubstance transfer device 700, could be a single-handled substancetransfer device, such as device 800 shown in FIGS. 16 and 17 anddescribed above.

Station 1000 includes substance transfer guide structure 1500 includingelongated guide supports 1502, 1504, 1506 having formed therein guideholes 1510, 1512, 1514, respectively. Each guide support includesstand-by holes formed at opposite ends thereof, but only stand-by holes1524 are visible on guide support 1502, because the substance transferdevices 700, 720 are located in the stand-by positions on guide supports1504 and 1506. Each substance transfer device 700, 720 includes guiderods (not shown) extending downwardly from its respective frame member702, 722 to engage guide holes 1510 and 1512 or 1512 and 1514, asdescribed above, to position the device 700, 720 with respect to eitherthe receptacle holding assembly 200 or the contamination limitingelement holding assembly 300. Because the substance transfer devices700, 720 only include manifolds 708, 728, respectively, which arealigned with the respective guide rods of each device, the guidesupports 1502, 1504, and 1506 only need guide holes 1510, 1512, and 1514that are aligned with each of the rows 260 of receptacles and rows 360of contamination limiting elements. Accordingly, for the illustratedembodiment, only ten guide holes 1510, 1512, and 1514 are needed, asopposed to the twelve guide holes 510, 512, 514 needed for theembodiment of FIG. 6, which is adapted for use with the dual functionsubstance transfer device 400, including the off center dispensermanifold 440.

It will be realized that the foregoing preferred specific embodiment ofthe present invention has been shown and described for the purposes ofillustrating the functional and instructional principles of thisinvention and are subject to change without departure from suchprinciples. Therefore, this invention includes all modificationsencompassed within the spirit and scope of the following claims.

1. A substance transfer device for simultaneously dispensing substancesinto and removing substances from two or more receptacles, saidsubstance transfer device comprising: (a) a support member; (b) asubstance dispensing apparatus operatively mounted to said supportmember and including two or more conduits, said substance dispensingapparatus being constructed and arranged to simultaneously dispensesubstance through each of said two or more conduits of said substancedispensing apparatus into each receptacle of a first set of two or morereceptacles; (c) a substance removing apparatus operatively mounted tosaid support member and including two or more conduits, said substanceremoving structure being constructed and arranged to simultaneouslyremove substance through each of said conduits of said substanceremoving apparatus from each receptacle of a second set of two or morereceptacles, wherein said substance transfer device is constructed andarranged to remove substance from each of the receptacles of the secondset with said substance removing apparatus at about the same time saidsubstance dispensing apparatus is dispensing substance into each of thereceptacles of the first set.
 2. The substance transfer device of claim1 further comprising a pair of handle members operatively mounted tosaid support member to facilitate handling of said substance transferdevice by a user.
 3. The substance transfer device of claim 1, wherein aportion of each of said conduits of said substance removing apparatusdefines a contamination limiting element engaging structure constructedand arranged to operatively engage a contamination limiting element forlimiting contact between said substance removing apparatus and apotentially contaminating substance removed by said substance removingapparatus from the two or more receptacles of the second set.
 4. Thesubstance transfer device of claim 3, further comprising a contaminationlimiting element disengaging structure operatively associated with saidsubstance removing apparatus and constructed and arranged to selectivelydisengage each of the contamination limiting elements engaged by saidcontamination limiting element engaging structures.
 5. The substancetransfer device of claim 1, further comprising handle structure mountedto said support member and adapted to permit manual manipulation of saidsubstance transfer device.
 6. The substance transfer device of claim 1,further comprising positioning structure mounted to said support memberand constructed and arranged to engage a portion of a structuresupporting the receptacles of the first and second sets of receptaclesto position said substance dispensing apparatus for dispensing substanceinto the receptacles of the first set and to simultaneously positionsaid substance removing apparatus for removing substance from thereceptacles of the second set.
 7. The substance transfer device of claim5, further comprising positioning structure mounted to said supportmember and constructed and arranged to engage a portion of a structuresupporting the receptacles of the first and second sets of receptaclesto position said substance dispensing apparatus for dispensing substanceinto the receptacles of the first set and to simultaneously positionsaid substance removing apparatus for removing substance from thereceptacles of the second set.